This invention relates to a method of and apparatus for transporting particulate materials from a lower level to a higher level, for example gold and other mined ores or construction debris.
It is known to use pseudoplastic flotation fluids in the pumping of materials of suitable particle size, for example drilling debris in an oil well. While this technique might in theory be used to transport ores and other solids from the working level of a mine to the surface, rather than using conventional mechanical lifting gear, in practice the energy requirements are too great to make the technique a practical proposition.
In general the currently-utilised method of moving gold and other mined ores or construction debris to surface is by means of single or multi-stacked ore skips as hoisted by wire rope with surface located winding gear powered by whatever required motive force via purpose designed control equipment. This method has in passing to carry the non productive weight of the skips and their stacking frame plus the weight of the hoisting wire rope, with allowances for the overcoming of inertia and associated friction forces. A multi-skip hoist shaft can also require extra area over that for man-riding cages and equipment hoists as might be obviated if ore could be pumped to surface. Whilst it is known that ore at suitably ground down size can be pumped in a fluid of higher density than water so as to be able to hold the particulate in suspension, this imparts hydrostatic and surge forces on such pumps which increase with depth. Where a sudden stoppage in flow occurs, this can create at restart many time-consuming problems in such systems.
All metal mines and some civil construction works utilise water at their mining or rock excavation level, whether for the drilling of diamond cored mineral or rock samples or for general cooling and dust control from percussion drilling and blasting. The liquid residue of such methods can be utilised for the mixing of hydraulic ore hoist fluid as afterwards recycled within the working zone prior to any excess being pumped back to circuit or to surface from a gravity fed sump located at base of access shaft.
Background prior art is indicated by GB-A-2 047 818, GB-A-1 543 817, EP-A-0 194 498 and U.S. Pat. No. 5,069,583.
The invention provides a method of transporting particulate materials from a lower level to a higher level, comprising:
establishing a flow loop comprising a closeable chamber for receiving batches of the particulate materials, a first flow conduit extending upwardly from the chamber to a delivery level, a second flow conduit extending upwardly from the chamber to a header tank located at a higher level than said delivery level, and valve means at the chamber for selectively isolating the chamber from the first and second flow conduits;
filling the flow loop with a pseudoplastic flotation fluid;
operating the valve means to isolate the chamber from the first and second flow conduits;
introducing a charge of the particulate materials into the chamber and then closing the chamber;
operating the valve means to connect the first and second flow conduits to the chamber; and
maintaining a supply of fluid in the header tank such that fluid and entrained particulate materials flow from the chamber through the first flow conduit to the delivery level.
The invention also provides apparatus for transporting particulate materials from a lower level to a higher level, comprising:
a flow loop comprising a closeable chamber for receiving batches of the particulate materials, a first flow conduit extending upwardly from the chamber to a delivery level, a second flow conduit extending upwardly from the chamber to a header tank located at a higher level than said delivery level, and valve means at the chamber for selectively isolating the chamber from the first and second flow conduits;
a pseudoplastic flotation fluid filling the flow loop;
means for introducing a charge of the particulate materials into the chamber and means for closing the chamber; and
means for separating the particulate material from the fluid discharged at the delivery level and for returning the fluid to the header tank.
Thus, the invention provides for the transport of ores, minerals and the like in a stream of purpose designed flotation fluid by means of an upper and lower interconnected U tube with an ore loading chamber just below the base of the upper U tube, this and the lower U tube being controlled by a multi-function valve whose hydraulic jack components are able to utilise the same flotation chemical, preferably at a higher concentration, which can simultaneously lubricate all other moving parts of the valve apparatus for use in that method.
The ore loading chamber can be formed in situ as a rock pressure vessels. Also, the two limbs of the upper U tube can be formed as drilled holes at the edge of or beyond the edge of any mine or tunnel access shaft, preferably in a manner which allows the drilling bit to be removed from within its drilling drive tube to allow an onward sealed in situ use as the pressurisation and hoisting ducts to such an ore loading chamber. Such methods of formation are known from U.S. Pat. Nos. 4,950,034 and 4,878,549.
In considering the utilisation of a hydraulic method of ore or tunnel debris hoisting or horizontal transportation the further reuse of whatever water is existent at the salient location the primary objective where the continuous pumping of minerals of higher specific gravity than water poses not only the problem of their suspension during the pumping process but also their chemical compatibility with the purpose designed flotation fluid as mixed with water having whatever pH and minerals content. By the use of a double U tube to continuously eject ore in a stream of suspending biodegradable pseudoplastic fluid having a design able to accommodate wide ranges of pH and minerals content offers additional advantages:
the reuse of liquid run off from other in-mine systems;
the partial use as an ore lixiviant during its transportation phase;
can be utilised as the hydraulic fluid element of recycled treated ore as stowed mine fill with or without uncontaminated cementitious addition; and
also able to be diluted to water viscosity for general mine use.
Preferably according to the present invention there is provided a method of operating a chain linked high pressure valve apparatus at the intersection of an upper and lower U tube, comprising an outer multi-valve common housing with at least nine entrants one of which is fitted with a double cone type valve allowing the sequence tensioned movement of a chain of a type exhibiting zero elongation via a third unvalved internal entrant carrying a sliding section of the apparatus having three separated aperture alignment type valves as allow the double U tube system to eject either the ore in suspension or recycle the suspension devoid of ore where this element of cycle allows any desanding or chemical beneficiation. Also, at higher mine level or at ground level of a set of synchronised lower pressure standard valves is preferably provided, connecting into the top of the longer U tube limb to allow this to impart a larger hydrostatic head to that in shorter U tube limb, both limbs connecting to the flotation fluid pumping or gravity supply pipework such as to allow a cyclic operation via a closed pre-set pressure control loop. Alternatively, an open gravity-controlled overspill calibrated excess hydraulic head arrangement incorporates an open or closed fluid volume control funnel at top of longer U tube limb, where in the gravity-assisted case a reciprocal raising and lowering of a weighted vessel by use of a wire rope can effect control of volumetric symmetry between the longer and shorter U tube limbs as retains their pre-calculated differential head. Additionally, a secondary utilisation this wire rope can be used to open the gravity weight assisted cone valve in the lower level commonly-housed control apparatus, this being otherwise moved by either a single or double high pressure hydraulic jack, utilising the same biodegradable pseudoplastic flotation chemical at an increased concentration as hydraulic fluid by which to effect a reciprocal movement with or without assistant gravity ballast weights of the sliding ram type multi-apertured valve which forms a preferred feature of the apparatus of the invention.
Preferably, at lower mine level the valve apparatus within its common housing has a short enlarged vertical section separating an upper and lower coned valve seat where a solid centralised rod below this enlarged section allows movement of gravity weighted two way coned valve end carrier. Any non-seated position produces circulation of flow into the lower pressuriseable ore-loading chamber, which can be sealed off for such purpose by means of a tensioned link chain connected to a single or reciprocating hydraulic ram in a manner that produces closure by either of the higher or lower engaged cone type valves. In this way flow continuation of fluid or ore fluid mixture is allowed upwards from the base of the lower U tube during the filling of loading chamber at atmospheric pressure. The selected cyclic flow status is achieved by the gravity weighted link chain assisting positioning of a sliding piston element within the common housing via intermediate action of a rocking sprocketed unit of small enough radius to move in an arc between fixed stops set into the common housing, thereby providing by piston sliding action the alignment of any one of three apertures in this element of apparatus as disposed at whatever angle to achieve safe cyclic non surge flow.
At apparatus level preferably a separately-attached high pressure hydraulic jack or jacks are set into the common housing at such angled position as to obtain a thrust reaction from the adjacent rock face by which to effect sequential positioning of the sliding piston within the valve apparatus common housing. The middle aperture of the housing preferably has a through bore allowing passage of the ore from the lower U tube upward into the shorter U tube limb above the control apparatus en route to its discharge elevation, the adjacent aperture in the direction of the longer U tube limb being able to promote flow through the upper U tube when devoid of ore by which to provide surgeless continuity of ore hoisting during closed-off reloading of ore from gravity discharging mine level dry ore chute at atmospheric pressure. This action is effected simultaneously with activation of the adjacent double cone valve together with positioning of furthest of the three apertures from longer U tube limb to give a connection from the lower U tube by gravity flow into the sump below the base of lower U tube bend, where the sump volume is larger than that of the entire fluid circuit to allow its use for evacuation of all fluid with or without ore from the system for either safety or maintenance reasons. The sump may also be gravity fed during ore loading, from an overflow valve set into the common housing below the enlarged section housing the double cone valve and the top of the loading chamber which has a separately sealed valve for ingress of ore. This is also able to be sealed by means of a jacked down valve using rock as its reactant force where these and any additional radial jacks that are used to stabilise the loading chamber about its centroid to have jack seatings as allow removal of the jacks for periodic maintenance.
Separate safety and operational functions of the double U tube system may include complete fluid evacuation of the system effected by a combined vacuum and pressure subsidiary pumping loop located at the level of the multivalve control apparatus and which negates the need for any valve protrusions within the U bend. The construction of the apparatus within a thick wall casting is able to accommodate oversizing due to metal loss from ore scour. A venturi-induced siphon can be effected by the separately operating sump pump which recycles all overflow fluid from the ore-loading phase of the cycle at a steady pumping rate back into the longer U tube limb above the control apparatus in such a way as to provide a replenishment of U tube systems motivating head imbalance. Separately valved sub circuits at ore discharge elevation can produce laminar or venturi induced vacuum related flow for the optimised use of necessary hydrocyclones able to remove fine ore particles prior to addition or beneficiation of flotation chemical or even to provide a final jetting action to any blockage at ore discharge point.
By way of an additional hydraulic circuitry control, the end cap incorporating the maintenance entry to the apparatus may also incorporate the control pipework and inbuilt pre-sealed entrant to expandable ring seals system by which to ensure against any small ore particles from the transportation stream being able to clog the sliding valve mechanism. By the continuously imposed head of the longer U tube limb, self-cleaning is effected. The end cap may also incorporate valves able to record and dissipate any induced negative or positive air or fluid pressures present in the cyclic system, these further negating the incidence of any surge condition where any flow cessation would manifest a smoothly changing rheological status.
Assistant elements may be included to assist the functioning of the sliding valve element of the control valve. For example, this can also utilise one or more bearing surfaces either as rails or grooves by which to guide and centralise the sliding portion of the valve, such bearing surfaces having gaps at the ring seal positions in the form of radial grooves able to accommodate the deflated ring packers during movement of the sliding element to any aperture position. A secondary set of ring seals can be set into a solid ring ledge forming part of the common housing these of either inflatable or compressive expansion type, the latter form taking advantage of the available jacking force. The jacks themselves would be motivated by hydraulic hoisting fluid rather than oil, since this might upset cyclic balance of pH and viscosity factors. The jack housings may be fitted with purpose-designed replenishable jacking consistency pseudoplastic fluid reservoirs at required overpressure to the salient hydrostatic head in the ore hoisting system where all periodic mechanical maintenance would be accomplished via an apparatus end cap.
As the motivating force element of the total cyclic system, the imbalance between the longer and shorter U tubes provides a hydraulic jacking effect by which the ore placed in the loading chamber is forced into U tube bend at its lowest level by the superimposed hydrostatic head from the upper U tube. This is then shut off from lower U tube after each batch of ore has passed through the systems multi-valve control apparatus for its upward transportation to surface treatment plant, where after each such cyclic action the loading chamber holds an element of the flotation fluid equal to the displaced volume of exuded ore, a similar amount of fresh ore then being placed dry by tremie tube into the loading chamber. During loading of the chamber, the ore displaces its own volume of fluid via a separate valve to a lower holding sump, where a pump at the lowest level of the cyclic system then transfers the excess flotation chemical up to the holding reservoir at the head of the longer U tube limb which has a sufficient cubic capacity and height above the discharge end of the shorter U tube limb to promote a gravity flow under the action of the imbalance between the two limbs. The whole cyclic system is thus powered by only the sump pump, which can be of sufficient size to drive any upper fluid circulation elements relating to the mixing and beneficiated recycling of salient flotation chemical dosages.